Field of the Invention
The present invention relates to a display device that can improve image quality.
Discussion of the Related Art
Various kinds of flat panel display devices that can replace heavy and bulky cathode ray tubes (CRTs) have been recently developed. Examples of the flat panel display devices are a liquid crystal display device, a field emission display device, a plasma display device, and an organic electro-luminescence display device.
Among the various kinds of display devices, a liquid crystal display device (LCD) is a device for displaying an image using a principle in which each pixel of a liquid crystal panel disposed on a front face of the LCD acts as a type of optical switch to selectively transmit a light generated from a light source of a backside thereof, e.g., a backlight unit. In comparison of a related art cathode ray tube (CRT) to an LCD, the related art CRT controls brightness by adjusting the intensity of an electron beam, whereas the LCD controls the brightness of image by adjusting the intensity of light generated from the light source.
Meanwhile, as the image technology has been developed more and more, technology which can display a motion picture as well as a still picture can be embodied in the LCD.
However, it is not easy to implement a motion picture well in the LCD. That is, since the response speed of a liquid crystal is slower than a frame period of the LCD, there occurs a motion blurring when applying a voltage newly in a next frame after a predetermined voltage, e.g., an image signal or a data voltage, previously charged at the liquid crystal is maintained for one frame. After all, the data of the previous frame has an effect on the data of the next frame, causing the motion blurring phenomenon to occur.
In particular, this motion blurring phenomenon strongly occurs when displaying the motion picture rather than the still picture.
FIG. 1 is a graph illustrating a light intensity versus a time in a related art CRT, and FIG. 2 is a graph illustrating a light intensity versus a time in a related art LCD.
Referring to FIG. 1, the CRT is driven by an impulse type. In this case, since the data is displayed for only an extremely short time during each frame period, the data displayed for only the extremely short time does not have an effect on a next frame period.
Referring to FIG. 2, the LCD is driven by a hold type. In this case, the data is continuously maintained for each frame period so that the data maintained during a previous frame period has an effect on a next frame period. Consequently, the motion blurring phenomenon inevitably occurs in the related art LCD which is driven by the hold type.
In order to prevent the motion blurring phenomenon, there has been proposed a black data insertion (BDI) method in which actual image data is applied only during a predetermined period of one frame and black data is applied during the other period of the one frame. Herein, the black data means the data voltage corresponding to a black gradation, e.g., 0 gradation. Therefore, the motion blurring phenomenon does not occur because each pixel displays the black gradation due to the black data.
FIG. 3 is a schematic view illustrating the BDI method in a related art LCD.
Referring to FIG. 3, an image data voltage and a black data voltage are alternatingly applied to a liquid crystal display panel during one frame period.
For instance, if there exist 488 number of gate lines, first to fifth gate lines are sequentially activated so that the image data voltage is applied to pixels of each activated gate line. Thereafter, the first to the fifth gate lines are activated again so that the black data voltage is applied to the pixels of each activated gate line.
Subsequently, sixth to tenth gate lines are activated so that the image data voltage is applied to pixels of each activated gate line and the image data is displayed on a screen. Afterwards, the sixth to the tenth gate lines are activated again so that the black data voltage is applied to the pixels of each activated gate line.
Such an operation is performed repeatedly for one frame period in which 488 number of gate lines are activated. Likewise, the same procedure is also performed during a next frame period.
In the related art LCD, the black data is supplied to a data driver after it is generated in a timing controller. That is, the black data is generated in the timing controller and various circuits should be additionally employed to provide the black data generated from the data driver to the liquid crystal display panel on a desired timing. As a result, the overall circuit becomes too complicated.